This invention relates to intraocular lenses (IOLs) and to methods for producing IOLs. More particularly, the present invention relates to very straight forward and easy to practice methods for producing IOLs with optics comprising polymeric materials, for example, silicone polymeric materials. IOLs produced in accordance with the present invention have advantageous properties, for example, outstanding fixation member pull strengths, that is advantageously large bond strengths between the optic of the IOL and the fixation member or members of the IOL.
The use of IOLs to improve vision and/or to replace damaged or diseased natural lenses in human eyes, particularly natural lenses impaired by cataracts, has achieved wide acceptance. Accordingly, a variety of IOLs has been developed for surgical implantation in the posterior or anterior chambers of the eye according to a patient's needs.
Known IOLs comprise an optical lens portion or optic which includes an optical zone, and one or more, preferably two, supporting structures, called fixation members or haptics, for contacting eye tissue to fix or hold the IOL in the proper position after implantation. The optic may comprise a soft, resilient material, such as a silicone polymeric material (in particular, an elastomeric cross-linked silicone polymeric material), an acrylic material and the like. The haptics typically comprise a filament constructed of a resilient metal or polymeric substance, such as polymethylmethacrylate (PMMA), polyamide, polypropylene and the like.
Each of the filament haptics is preferably flexible to reduce trauma to sensitive eye structures and to be yielding during insertion of the IOL. In addition, filament haptics generally have a memory retaining capability, e.g., springiness, so that after implantation of an associated IOL, the filament haptics automatically tend to return to their normal orientation.
Although the filament haptics are very useful, certain difficulties remain. For example, filament haptics and soft or deformable optics tend to be formed from dissimilar materials which do not ordinarily chemically bond together. As a result, filament haptics have been designed having a variety of enlarged attachment end configurations or structures, e.g., anchor structures, for providing a physical or mechanical interlock between the haptic and optic. Polypropylene haptics, for example, have been secured into silicone polymer-based optics by means of a mechanical lock. This lock may comprise a small loop or other anchor formed at the attachment end or lens bonding region of the haptic, which is then placed in a mold. The precursor material of the silicone polymer-based optic is poured into the mold, through and/or around the lens bonding region of the included haptic or haptics, and is then cured. Christ et al U.S. Pat. No. 4,790,846 discloses the molding of an optic around a haptic having a small loop or other anchor to effect a secure haptic connection.
Christ et al U.S. Pat. No. 4,790,846 further discloses a method for making an IOL in which a region of an elongated filament haptic has a different configuration, e.g., a bulbous enlargement, which cooperates with the optic of the IOL to form a mechanical interlock between this different configuration and the optic. If desired, the bulbous enlargement may have its outer surface roughened to improve adhesion of the material of the optic.
Kaplan et al U.S. Pat. No. 4,668,446 discloses securing a haptic having an enlarged portion to an IOL by swelling the lens material having a drilled peripheral bore with an organic liquid or vapor. After the enlarged portion of the haptic is inserted into the peripheral bore of the lens, the organic fluid is removed.
In general, the use of enlarged attachments, configurations and portions makes it more difficult, complex and time-consuming to produce IOLs. For example, such enlargements must be produced or formed on the haptic before the haptic is attached to the optic. This additional step is costly and time-consuming. It would be advantageous to obtain effective haptic/optic securement and pull strength without the need for such enlarged attachments, configurations and portions.
Blake et al U.S. Pat. No. 5,104,590 discloses improving the adhesive properties of polypropylene haptics to silicone lenses through surface treatment of the haptic with a combination of a high frequency corona discharge and a silicone primer. Christ et al U.S. Pat. No. 5,147,397 discloses exposing the lens bonding region of the haptic to a plasma at conditions effective to enhance the bondability of the lens bonding region to the optic. While these procedures can be effective in enhancing haptic/optic bond strength, they are relatively sophisticated and are relatively expensive to practice, thus adding to the complexity and cost of producing IOLs. In addition, substantial care must be exercised in controlling the corona discharge and plasma exposing procedures to avoid damaging the relatively fine filament haptics.
Doyle et al U.S. Pat. No. 5,423,929 discloses bonding a fixation member to an optic of an IOL using a primer component coated on the fixation member. Using this system, good fixation member optic bond strengths are obtained. However, these methods do involve a step of placing a primer component on the fixation member. Also, the presence of the primer component or a residue thereof in the eye (with the final IOL) may have some potential impact on the IOL patient.
It would be advantageous to provide a more straight forward and easy to practice method of producing IOLs which effectively enhances the bond or pull strength between the fixation member or members and the optic.